The present invention relates to construction method for widening road, superhighway or railway tunnels, without interrupting traffic flow.
Due to the continuously increasing traffic demands, it is frequently necessary to widen roads, superhighways or railways in order to improve their traffic handling capabilities.
Even if this problem can be solved in a comparatively easy manner, in the case of transport routes which run entirely on the surfaces, the solution of this problem is very complex and nearly impossible when the routes pass through tunnels.
In fact, widening a tunnel involves great problems mainly related to the discomfort and safety of the users, as well as technical and operating problems related to works to be performed in a ground already disturbed by a previous boring or excavation, in addition to problems related to the stress-strain conditions occurring as the widening operations are carried out.
Accordingly, the aim of the present invention is to solve the above mentioned problems, by providing a construction method that allows road, superhighway and railway tunnels to be widened without interrupting traffic flow.
Within the scope of the above mentioned aim, a main object of the present invention is to provide such a construction method which is very safe for the users, while reducing to a minimum the user inconvenience.
Another object of the present invention is to provide such a construction method which is very flexible in that it can be employed in any type of ground and stress-strain condition that occurs as said method is carried out.
Another object of the present invention is to provide such a construction method which guarantees the observance of work schedules specified in the design, independently of the type of ground and stress-strain conditions involved, while reducing and reliably planning construction costs and times, and also reducing to a minimum traffic deviations and consequent user inconvenience.
Another object of the present invention is to provide such a construction method specifically designed for solving the problem of the possible presence, around the original cavity, of a band of ground which has been already plasticized and which must not be further disturbed.
Yet another object of the present invention is to provide such a construction method that allows to cross section of a tunnel to be widened without causing any damaging deformation in the ground to be triggered, which would in turn cause very strong pressure on the lining of the final widened tunnel, and result in differential surface settlements very dangerous for surface constructions above.
According to one aspect of the present invention, the above mentioned aim and objects, as well as yet other objects, which will become more apparent hereinafter, are achieved by a construction method for widening road, superhighway or railway tunnels, without interrupting the traffic flow, which is characterized in that said construction method comprises:
a first stage in which the ground between the theoretical profile of the future widened tunnel and that of the original tunnel is excavated in steps, and
a second stage in which the final lining, consisting of one or more arches of prefabricated segments is placed in steps, close to the face, and prestressed in order to provide an immediate confinement pressure against the ground behind it.